In recent years, attention is being given to a nonvolatile semiconductor memory device that employs ReRAM (Resistive RAM) in a cross-point type memory cell, the ReRAM having a structure where an oxide film is sandwiched above and below by an electrode. This memory cell sometimes combines the ReRAM with a rectifying element of a diode or the like.
Operations of this memory cell include a setting operation in which a certain setting voltage being applied to the electrodes above and below the oxide film causes a resistance value of the oxide film to be lowered, and a resetting operation in which a certain resetting voltage being applied causes the resistance value of the oxide film to be raised. In addition, it is also required that, in an initial process, forming is executed, forming being to form a current path in the oxide film in order to make these setting operation and resetting operation possible.
When these operations or forming are executed in a certain selected memory cell, a bias state is created in a memory cell array to prevent these operations or forming from occurring in other unselected memory cells, the bias state being such that a bias in a reverse direction of the diode is applied to the unselected memory cells. However, in this case, a reverse direction current gets generated in the unselected memory cells, and when circuit scale becomes large, size of the reverse direction current becomes unable to be ignored. The problem becomes particularly great in forming, because a larger reverse direction bias is applied in forming than in the setting operation and resetting operation.